Consider the Bruce Lee film Game of Death.
In it, he must fight his way UP through several guardians before reaching the final room. (Each level has a symbology, but that's not important here.)
Essentially its a dungeon in reverse.
So, just take a dungeon idea you have, flip it upside down, and set it in a wealthy merchant's fortified mansion.
Or a Wizard's Tower...or a mill, or whatever.
Ah! If you can, track down and read the Thieves' World books...or, considering your timeline, the RPG campaign setting. 90% of that series was set in the confines of cities. Even if you don't have much time, though, track down the books. They are collections of short stories, so you should be able to read a couple of them in time to help you out.